<?php

$a=[1,2,3,4];
$b=[5,6,7,8];

$c=array_merge($a,$b);
print_r($c);

// Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 [6] => 7 [7] => 8 )